Filter Media

Hi All - curious on your opinions regarding blended multi-media vs layering. Like the old Provector/Reactor blend of Birm, Carbon, Cal-Cor and/or Filter AG - mixed together or layered? Would they tend to stratify anyway even if blended? I've been using a mixture of Centaur and Turbidex (Filter Ag Plus) lately which I typically mix together and it works well for iron, sulfur & general filtration but I wonder if after a few regens if it becomes separated. And then taking it a step further, what size DLFC should you use if one media requires 8-10 GPM/FT2 vs 14-18? I typically split the difference but maybe it would be better to go with the heaviest requirement and install an upper basket? Thanks!